This invention relates to hydrants or valves attached to municipal water systems, and in particular to a simple blow-off device for flushing portions of water systems.
The need for periodically flushing portions of water systems, particularly dead-ends in the systems, has been recognized for many years, as shown for example in Lazenby III, U.S. Pat. No. 4,756,479. A summary of many of the problems requiring such flushing, as well as of the traditional solutions to those problems, is contained in my co-owned U.S. Pat. No. 5,201,338. More recently, such flushing operations have been automated, as described in McCarty, U.S. Pat. No. 5,921,270. The McCarty patent is owned by a company related to the assignee of the present invention. A similar approach is described in Newman, U.S. Pat. Nos. 6,035,704 and 6,358,408. Other approaches are shown in Poirer, U.S. Pat. No. 6,062,259, and Esmailzadeh, U.S. Pat. No. 6,467,498, and in Taylor et al, published applications US 20040252556, US 20040238458, US 20040238037, and US 20040238028.
Although the prior art systems have met with success, the complexity of the systems, the time and effort required to install and use them, the difficulties attendant to removing and servicing them, and their consequent expense have limited their use.
In some situations, the initial cost of the flushing system outweighs the cost of operating it. In these situations, a simple blow-off system comprising an underground manual valve is provided, and water is flushed through an above-ground discharge pipe. The discharge pipe is commonly a 2″ or 3″ diameter piece of plastic pipe, such as PVC, with an elbow at its free end. These systems are generally fabricated on-site. It is desirable to provide a drain in the discharge pipe below the frost line. The valves commonly used for such installations (for example, resilient seat gate valves), however, do not include an automatic drain. An example of a resilient seat gate valve is that disclosed in Bottenfield, U.S. Pat. No. 6,663,079. Without a drain, water remaining in the discharge pipe downstream of the manual valve is liable to freeze and damage the discharge pipe. If a drain hole is drilled into the discharge pipe below the frostline, it is open at all times, causing erosion of surrounding soil and possible contamination of the water supply.